The decision has been branded unjust and unfair, particularly to those living in Europe.
Photograph: Lauren Hurley/PA

Up to 3 million Britons living overseas are to be denied a vote in the general election, the Cabinet Office has confirmed.

In a letter sent to the New Europeans campaign group on Friday, the Cabinet Office said that “unfortunately” British citizens who had lived abroad for longer than 15 years would not be entitled to vote on 8 June.

The letter has prompted a furious reaction from Britons living abroad, and in Europe in particular, with campaign groups accusing the Conservatives of breaking yet another promise.

Nathan Lappin of the constitution group in the Cabinet Office told New Europeans that “there is no sufficient time to change the relevant primary and secondary legislation to enfranchise all British expats, scrapping the 15-year time limit, ahead of the dissolution of parliament before the general election”.

The decision has been branded unfair, particularly to those living in Europe who will face life-changing challenges post-Brexit.

“The people most affected by the referendum were not allowed to vote in it, simply because they exercised their right to live in another country,” said Dave Spokes, one of the founders of the support group Expat Citizen Rights in EU. “Now it seems they will miss out again as their government has repeatedly failed to honour repeated promises to repeal this unjust and unfair rule.

“These people spent their lives working in the UK and many still pay taxes there. It is quite disgraceful that any government can so disregard so many of its citizens.”

Jane Golding, a British lawyer living in Berlin and campaigner for the rights of Britons abroad, said the promise has been broken twice as it was in the Conservative manifesto in the 2015 general election and the Queen’s speech that followed.

“So that is twice we have been denied the right to vote and to participate in the democratic process when this had been promised on an issue, leaving the EU, that directly affects our personal and professional status,” she said.

Last October the government promised to scrap the current 15-year time limit as part of a bid to strengthen ties with emigrants following the decision to leave the EU.

The plans followed a court battle spearheaded by the second world war veteran Harry Shindler, who fought in the Battle of Anzio in Italy in 1944. The 95-year-old, who moved to Italy to be near his grandson in 1982, has been unable to vote in the UK since 1997 but cannot vote in Italy either.

As recently as February, the constitution minister Chris Skidmore assured Shindler and others the government was on track, telling them “their stake in our country must be respected”.

In a written answer on the topic to the New Europeans founder Roger Casale, Skidmore promised “this government will not deny them the opportunity to have their say in how the country is governed”. He also revealed that the government estimated “a further 3 million British citizens resident overseas will be enfranchised”.

Samia Badani, director of New Europeans, said the decision not to expedite legislation was devastating for Britons desperate to have a say on their own futures in Europe but it was not too late to get them on the electoral register. “The time for legislation is now. When there is a will, there is a way,” she said.

Badani said: “We are very disappointed – this is another broken promise. We have been campaigning for the removal of the 15-year rule – which is very arbitrary – for years. We were promised that at the next general election all UK citizens could vote, but it now looks like a double-whammy: they couldn’t vote in the referendum and now can’t vote in the next general election.”

The New Europeans group is demanding that the government rethink its position. It also wants a commitment from the government and the Electoral Commission to urgently target overseas residents who are eligible to register to vote. It believes tens of thousands of Britons abroad still have time to register, as the last time this happened more than 70,000 new voters were found.